1. Field of the Invention
The present invention relates to a gas replacement method and apparatus, and an exposure method and apparatus, which are used in the exposure process in, for example, the fabrication of semiconductor devices.
2. Description of the Related Art
Various exposure apparatuses have been used heretofore in manufacturing semiconductor devices, thin-film magnetic heads, liquid crystal displays or the like using the photolithography technology. A typical exposure apparatus among them projects the image of a pattern formed on a photomask or reticle (hereinafter called xe2x80x9cmaskxe2x80x9d) on a substrate whose surface is coated with a photosensitive agent, such as a photoresist, via a projection optical system. Due to the recent miniaturization of patterns to be projected on shot areas on a substrate, the wavelengths of illumination light for exposure (hereinafter called xe2x80x9cexposure lightxe2x80x9d) to be used are becoming shorter. In other words, exposure apparatuses that use a KrF excimer laser (248 nm) and ArF excimer laser (193 nm) are being made into practical use and are taking the place of those using a mercury lamp that has been popular. Further, there is an active development on exposure apparatuses that use an F2 laser (157 nm) in order to achieve further pattern miniaturization.
When vacuum ultraviolet rays having a wavelength of about 180 nm or lower are used as exposure light, the exposure light is attenuated and cannot reach onto the substrate with a sufficient intensity if a substance which has a strong light absorptive characteristic with respect to light of such a wavelength band, such as oxygen molecules, hydrogen molecules or carbon dioxide molecules, (hereinafter called xe2x80x9clight absorptive substancexe2x80x9d) is present in the optical path space where the exposure light travels. In this respect, exposure apparatuses that use vacuum ultraviolet rays are designed to improve the sealability of the optical path space where the exposure light travels, thereby blocking a light absorptive substance coming from outside, and perform a work of reducing the light absorptive substance present in the optical path space. Methods of reducing the light absorptive substance include a method of vacuuming the inside of the optical path space to reduce the internal pressure and then keeping the vacuum state, a method of filling the vacuumed space with a substance which shows low absorption characteristic with regard to exposure light (e.g., an inert gas such as helium, argon or nitrogen gas), and a method of supplying such an inert gas into the optical path space without vacuuming the space.
Typical masks have a transparent thin film called xe2x80x9cpelliclexe2x80x9d attached to the pattern surface in order to prevent adherence of dust or like to the pattern surface. When the aforementioned vacuum ultraviolet rays are used as exposure light, therefore, it is also necessary to reduce a light absorptive substance in the space that is formed between the pellicle and the mask. As the pellicle is easily damaged, it is hard to stably execute gas replacement of reducing the light absorptive substance in this space and supplying an inert gas there.
Accordingly, it is an object of the present invention to provide a gas replacement method and apparatus, and an exposure method and apparatus, which can stably and efficiently replace a gas in the space formed between a thin film and a substrate, such as a pellicle and a mask.
To achieve the above object, a gas replacement method according to one aspect of the invention adjusts the exhaust amount of a gas from a closed chamber which accommodates a substrate with which a thin film is provided so that deformation of the thin film due to the exhaust is within a predetermined range from the closed chamber.
According to the aspect of the invention, a substrate is accommodated in the closed chamber and the gas in the closed chamber is exhausted to thereby replace a gas in the space that is formed between the thin film and the substrate. As the exhaust amount of the gas from the closed chamber is adjusted so that the deformation of the thin film is within a predetermined range, stable gas replacement can be executed while preventing the thin film from being damaged.
In this case, the exhaust amount of the gas from the closed chamber is adjusted based on the result of measuring the deformation of the thin film, the thin film is surely prevented from being damaged at the time of carrying out gas replacement.
This gas replacement method can be realized by a gas replacement apparatus which comprises a closed chamber which accommodates a substrate with a thin film placed thereon; an exhaust device which is connected to the closed chamber and exhausts a gas from the closed chamber; a deformation measuring device which is associated with the thin film and measures deformation of the thin film; and a control system which is connected to the deformation measuring device and adjusts the exhaust amount of the gas based on the result of that measurement so that the deformation of the thin film is within a predetermined range.
The pressure in the closed chamber may be measured so that the exhaust amount is adjusted based on the result of that measurement. In this case too, the thin film is surely prevented from being damaged at the time of performing gas replacement.
This gas replacement method can be realized by a gas replacement apparatus which comprises a closed chamber which accommodates a substrate with a thin film placed thereon; an exhaust device which is connected to the closed chamber and exhausts a gas from the closed chamber; a pressure measuring device which is provided with the closed chamber and measures a pressure in the closed chamber; and a control system which is connected to the pressure measuring device and adjusts the exhaust amount of the gas based on the result of that measurement so that the deformation of the thin film is within a predetermined range.
As a replacement gas is supplied into the closed chamber, the replacement gas is supplied into the space that is formed between the thin film and the substrate. At the time of supplying the replacement gas into the closed chamber, at least one of the supply amount of the replacement gas and the exhaust amount of the gas is adjusted so that the deformation of the thin film due to the supply of the replacement gas is within a predetermined range. This can ensure stable gas replacement while preventing the thin film from being damaged. This can be accomplished by providing a gas supply device in the gas replacement apparatus, which supplies a replacement gas into the closed chamber, and allowing the control system to adjust at least one of the supply amount of the replacement gas and the exhaust amount of the gas from the closed chamber so that the deformation of the thin film is within the predetermined range.
According to another aspect of the invention, there is provided a gas replacement method for replacing a gas in a space formed between a substrate and a thin film to be provided with the substrate, wherein at the time of exhausting the gas from the space, the exhaust amount of the gas from the space is adjusted so that deformation of the thin film due to the exhaustion is within a predetermined range.
That is, the gas in the space formed between the substrate and the thin film may be replaced directly, in which case as the exhaust amount of the gas from the space is adjusted so that the deformation of the thin film is within a predetermined range, stable gas replacement can be executed while preventing the thin film from being damaged.
This gas replacement method can be achieved by a gas replacement apparatus which replaces a gas in a space formed between a substrate and a thin film to be provided with the substrate and comprises an exhaust device which exhausts a gas from the space; a deformation measuring device which measures deformation of the thin film; and a control system which adjusts the exhaust amount of the gas based on the result of that measurement so that the deformation of the thin film is within a predetermined range.
A replacement gas may be supplied into the space directly in which case stable gas replacement can be ensured by adjusting at least one of the supply amount of the replacement gas and the exhaust amount of the gas so that the deformation of the thin film due to the supplement of the replacement gas is within the predetermined range at the time of supplying the replacement gas into the space. This can be accomplished by providing a gas supply device in the gas replacement apparatus, which supplies a replacement gas into the space, and allowing the control system to adjust at least one of the supply amount of the replacement gas and the exhaust amount of the gas from the space so that the deformation of the thin film is within the predetermined range.
According to another aspect of the invention, there is provided an exposure method comprising the steps of accommodating a mask on which a protection member is provided via a frame into a closed chamber having at least one of a first space including an optical path of exposure light and a second space adjacent to said first space; replacing a gas in the closed chamber with a predetermined gas which demonstrates low absorption of the exposure light; replacing a gas in a space formed between the protection member and the mask with the predetermined gas according to replacing the gas in the closed chamber; and irradiating the exposure light onto the mask after the latter gas replacement and transferring an image of a pattern of the mask onto a substrate.
According to the invention, the mask is accommodated in the preliminary chamber and the gas in the preliminary chamber is replaced with a replacement gas to thereby replace a gas in the space formed between the protection member and the mask with the replacement gas. It is however possible to ensure stable gas replacement while preventing the protection member from being damaged, by adjusting the exhaust amount of the gas from the preliminary chamber so that the deformation of the protection member is within the predetermined range. As the mask is placed in the space that includes the optical path with a light absorptive substance in this space reduced, therefore, stable exposure is carried out.
This exposure method can be realized by an exposure apparatus which comprises a closed chamber which accommodates a mask on which a protection member is provided via a frame, the closed chamber having at least one of a first space including an optical path of exposure light and a second space adjacent to said first space; a gas replacement apparatus which is provided with the closed chamber and replaces a gas in the closed chamber with a predetermined gas which demonstrates low absorption of the exposure light; and a deformation measuring device which is associated with the protection member and measures deformation of the protection member.
According to another aspect of the invention, there is provided an exposure method comprising the steps of accommodating a mask on which a protection member is provided via a frame into a closed chamber having at least one of a first space including an optical path of exposure light and a second space adjacent to said first space; replacing a gas in a space formed between the protection member and the mask with a predetermined gas in the closed chamber; and irradiating the exposure light onto the mask after the latter gas replacement and transferring an image of a pattern of the mask onto a substrate.
According to the exposure method of the invention, with the mask accommodated in the preliminary chamber, the exhaust amount of the gas from the preliminary chamber can be adjusted based on a change in the pressure in the preliminary chamber at the time of replacing a gas in the space formed between the protection member and the mask with a replacement gas by replacing the gas in the preliminary chamber with the replacement gas. In this case, it is also possible to ensure stable gas replacement while preventing the protection member from being damaged, by adjusting the exhaust amount of the gas from the preliminary chamber so that the deformation of the protection member is within the predetermined range. As the mask is placed in the space that includes the optical path with a light absorptive substance in this space reduced, therefore, stable exposure is carried out.
This exposure method can be realized by an exposure apparatus which comprises a closed chamber which accommodates a mask on which a protection member is provided via a frame, the closed chamber having at least one of a first space including an optical path of exposure light and a second space adjacent to said first space; a gas replacement apparatus which is provided with the closed chamber and replaces a gas in the closed chamber with a predetermined gas which demonstrates low absorption of the exposure light; a pressure measuring device which is provided with the closed chamber and measures a pressure in the closed chamber; and a control device which is connected to the pressure measuring device and controls the gas replacement apparatus based on the result of measurement from the pressure measuring device so that the deformation of the protection member is within a predetermined range.
The exposure apparatus of the invention may be modified to comprise a closed chamber which accommodates a mask on which a protection member is provided via a frame, the closed chamber having at least one of a first space including an optical path of exposure light and a second space adjacent to said first space; a gas replacement apparatus which is provided with the closed chamber and replaces a gas in a space formed between the protection member and the mask with a predetermined gas which demonstrates low absorption of the exposure light; and a deformation measuring device which is associated with the protection member and measures deformation of the protection member.